The present invention may be understood in light of the following state of the art.
Ever since processes of converting crushed plastic bottles made of polyethylene terephthalate (PET) into fiber for textiles was proposed as a substitute for virgin polyester, attempts have been made to commercialize the processes. However, development of filaments, staple fiber, yarn, and fabric for the purposes of expanding the potential end uses of these fibers has been relatively limited. This has been attributed primarily to the inherently high cost of acquiring a clean raw material source. When one uses polymer made from the inherently impure post consumer recycled (PCR) polyethylene terephthalate (PCR-PET), one is limited to staple spun yarn rather than a continuous filament yarn because of the unpredictable weak points in monofilaments caused by the impurities. Practical uses for the staple spun yarn have been limited.
When particular domestic-based end use product manufacturers brought products containing fabric made from recycled plastic bottles to market and charged a premium for a product that had inherent quality deficiencies, they were unable to sustain significant enough market demand for these products to merit the expansion of plastic bottle fiber production. Instead, the fiber mills, which had originally predicted growth In market consumption of the fiber, were forced to close fiber plants that were originally supplying these domestic-based end use product manufacturers with their fiber.
Therefore, a longstanding need has existed for an economical method of utilizing PCR-PET to manufacture useable yarn of high quality.
Several highly cost-intensive PCR-PET purification methods now exist which are able to almost eradicate contamination from the recycled materials stream. They produce food-grade materials, and such materials might be suitable for producing continuous filament yarn. Because of their cost, however, they are not presently useful for producing commercially viable fiber.
The manufacture of yarn, whether in the form of thread or higher denier yarns, is one of the oldest technologies known. Numerous manufacturing methods are known for making continuous filament yarns, for combining continuous filaments into yarns, and for making yarns from shorter, staple fibers. Spinning staples into yarns has been known since prehistory.
Today, the three most popular spinning frames for staple spun yarn are ringspun, open end, and air jet. Prior to air jet, ringspun was considered the best in terms of quality and strength. Open end spinning has always been considered to be cheap and fast. Air jet is now hailed by most industry experts to be the optimal type of spinning frame for almost any application. Air jet spinning produces a fasciated yarn including a sheath of generally axially aligned staples bound together with discontinuous generally helical bundles of staples. Air jet machines are expensive; however their output speeds even at fine counts make them the best solution from an economic standpoint. From the standpoint of performance, the air jet produces the lowest pill yarn ever spun. The only complaint thus far is that the strength of an air jet yarn is slightly less than the strength of a ringspun yarn; however, this issue is easily overcome by placing a filament core inside the air jet yarn. The general rule for staple fiber going into air jet spinning frames is that it should be between about 1.2 and 2.0 inches (3 to 5 cm) in length, preferably between about 1.2 and 1.7 inches (3 to 4.3 cm) in length, and most preferably about 1.5 inches (3.8 cm) in length. Diameter of the staples can range from about 0.5 to about 2.0 denier per filament (dpf). A variant of an air jet spinning frame is known as a vortex spinning frame. A vortex spinning frame is capable of spinning a wider range of natural staple fibers, including cotton fibers, than is easily obtained with the earlier forms of air jet spinning frames. The vortex spinning frame produces a three-dimensional cotton sheath having better hand than does the basic air jet frame. It is also faster.
Air jet spinning frames are well known in the art. Air jet spinning is presently dominated by Murata Kikal KK of Kyoto, Japan. Its MJS air jet spinning machine, MTS twin spinning machine, and MVS vortex spinning machines are widely used and their details are known to those skilled in the art. Such machines are described for example in Oxenham, “Fasciated Yarns—A Revolutionary Development?” Journal of Textile and Apparel, Technology and Management, Vol. 1, issue 2, Winter 2001, pp. 1-7; Oxenham, “Developments In Spinning,” TextileWorld.com, May 2003; and in numerous patents, such as Shaikh et al., U.S. Pat. No. 6,405,519 ; Scheerer et al, U.S. Pat. No. 6,250,060; Scheerer et al., U.S. Pat. No. 5,960,621; Ota, U.S. Pat. No. 5,481,863; Griesshammer et al., U.S. Pat. No. 6,679,043; Shigeyarni et al., U.S. Pat. No. 6,655,122; and Mori, U.S. Pat. No. 6,370,858.
Other yarns include those in which a core is covered with a continuous filament helix using a covering machine (sometimes called coverwrapping machine or wrapping machine). These machines are traditionally used to cover spandex or other continuous filament stretch yarns. A single or double helix is applied by a standard covering machine. Covering machines are occasionally used to cover non-stretch continuous filament cores to produce “fancy” yarns for small niche markets or industrial yarns. Such machines are sold by a number of manufacturers, for example by Rieter/ICBT, now known as the Filament Yarn Technologies Group, of Rieter Machine Works, Ltd., Winterthur, Switzerland. They are also widely described in the patent literature, for example in Siracusano, U.S. Pat. No. 4,350,731; Tillman, U.S. Pat. No. 4,137,698; and Payen, U.S. Pat. No. 4,525,992.
Continuous filament yarns are sometimes texturized (also called textured) by a texturizing machine to give them particular surface or geometrical properties. For example, a filament may be given a “false twist” by twisting it, heating it, cooling it, and then untwisting it, or it may be given a more random shape by the several high-speed air methods described in Bertsch et al., U.S. Pat. No. 6,088,892. l Surface features are given by other methods, known to those skilled in the art. Generally, texturizing yarn filaments is done for the purpose of giving a synthetic (plastic) yarn some of the characteristics of a natural fiber.
Synthetic yarns are generally superior to yarns made of natural fibers in tenacity (tensile strength), abrasion resistance, quick-drying properties, and dimensional stability, but they generally lack the hand, drape, and moisture absorbance of their natural fiber counterparts. It is frequently desirable to produce yarns having special characteristics such as fire retardancy, high moisture permeability, bacterial resistance, ultraviolet ray resistance, low surface friction, or special aesthetic texturing. Generally, providing one of these characteristics requires compromising other characteristics of a synthetic or natural yarn. For example, high tenacity synthetics such as polyarnides including aromatic polyarnides (aramids) and high-tenacity aliphatic polyarnides (nylon), carbon, or glass provide much higher tenacities than many other synthetics or most natural fibers, but they lack many desirable characteristics as a yarn for numerous fabrics. Aramids provide greater tenacity than high-tenacity nylons, but they are susceptible to ultraviolet radiation. Providing other characteristics in a high-tenacity synthetic yarn generally reduces the tenacity of the yarn.